Return chicken, bone side down, to pot. Reduce heat to a simmer, cover, and cook until chicken is tender and cooked through, 30 to 35 minutes. Transfer chicken to a plate; loosely tent with aluminum foil to keep warm. Add tomatoes to pot; season with salt and pepper. Cook on high until sauce has thickened, 6 to 8 minutes. Reduce heat to medium-low, and return chicken to pot; cook until heated through. Serve, garnished with tarragon, if desired.